This invention relates to an adjustable regulator for developing a proportional reaction signal to produce a variable gain between an input force provided by an operator and a operational force supplied by a brake booster to a master cylinder to effect a brake application.
In hydraulic brake boosters of a type disclosed in U.S. Pat. Nos. 4,441,319 and 6,226,993, a control valve is moved by an input force applied to a brake pedal by an operator to regulate the flow of pressurize fluid from a source to an operational chamber. The regulated pressurized fluid acts on a power piston to provide.and operational force that moves pistons in a master cylinder to pressurize fluid that is supplied to wheel brakes to effect a brake application. A reaction force produced by boost pressure in the movement of the power piston is transmitted back to the brake pedal to balance the input force such that the operational force supplied to move the pistons in the master cylinder is a linear function of the input force applied to the brake pedal.
The structure in hydraulic brake boosters of a type disclosed in U.S. Pat. Nos. 4,281,585; 4,539,892; and 4,625,515 while similar in producing an operational force is different in that a housing has a first and second bores connected to a pressure chamber with a power piston located in the first bore and a control valve located in the second bore. The control valve is connected to the brake pedal by a lever arrangement connected to the power piston. An input force applied to the brake pedal causes the lever arrangement to pivot about the power piston and move the control valve to allow pressurized fluid to flow into the pressure chamber. The pressurized fluid acts on the power piston to move pistons in a master cylinder and develop a pressurized fluid that is supplied to the wheel brakes to effect a brake application. A reaction force produced by the movement of the power piston is transmitted back to the brake pedal back from the power piston to the brake pedal to balance the input force such that the output force produced is a linear function of the input force applied to the brake pedal.
While the above prior art hydraulic brake boosters function in an adequate manner, the control valve, lever arrangement, input member and powers piston are all exposed to pressurized fluid during a brake application resulting in a need to provide for high pressure seals with respect to all openings and sliding surfaces. Structure has been disclosed in co-pending U.S. patent application Ser. No. 09/894,106 whereby the lever arrangement and input member are isolated from the pressurized fluid.
It has been suggested those additional features such as traction control, dynamic operational control and anti-skid control are desirable in a hydraulic brake booster to provide a total brake system. However, as the brake pedal in such hydraulic brake boosters mirrors the movement of the power piston additional structure is needed to hold the brake pedal stationary during a functional performance relating to such additional features. One way to hold the brake pedal stationary during such additional functions is disclosed by the structure in U.S. Pat. No. 6,203,119 wherein a control valve seat moves while the input member remains in a stationary position to meter operational pressurized fluid from a secondary source to effect a brake application.
A primary object of the present invention is to develop a variable gain between an input force applied by an operator to a push rod and a operational force supplied by a brake booster to a master cylinder to effect a brake application.
According to this invention, a hydraulic brake booster for use in a brake system has a housing with a first bore therein separated from a second bore. The first bore is connected to the second bore by a passage and the second bore is connected to a source of pressurized supply fluid. The first bore retains a power piston and the second bore retains a control valve. An input member connected to a brake pedal is connected to the power piston and linked to the control valve by a lever arrangement. The lever arrangement transmits an actuation force derived from an input force applied to the input member to operate the control valve and allow controlled pressurized supply fluid to be communicated from the second bore through the passage to the first bore. The controlled pressurized supply fluid supplied to the first bore acts on the power piston to develop an operational force that is supplied to move pistons in a master cylinder to effect a desired brake application. The first bore is also connected to a stepped bore that retains an adjustable regulator means characterized by first and second restricted orifices that are created by locating surface configuration on a shaft with respect to corresponding surfaces in the stepped bore. A portion of the controlled pressurized supply fluid that is supplied to the actuation chamber is communicated to the stepped bore and flows through the first and second orifices to a reservoir. In flowing through the first and second orifices, the controlled pressurized supply fluid experiences a pressure drop and it is this pressure of the fluid as present in the stepped bore between the first and second orifices that is communicated as a proportional reaction signal to act on the input member to balance the input force applied to the brake pedal by the operator. This functional operation results in an operational force created by the controlled pressurized fluid acting on the power piston which has a variable gain with respect to the input force applied to the input member by the operator to effect a brake application.
An advantage of this invention resides in a brake booster wherein a reaction force received by an operator during a brake application varies as a function of the controlled pressurized fluid supplied to a power piston to develop an operational force.
A further advantage of this invention resides in the ability to adjust a gain of input force applied to a brake pedal with respect to an operational force produced by a brake booster.